System and method for tracking shipment of items utilizing RFID-tags

ABSTRACT

A system and method of tracking a plurality of mail units during transfer from a source location to a destination. One embodiment is a method comprising associating information identifying the plurality of mail units with a radio frequency (RF) tag that identifies a carrier unit. The method further comprises storing said associated information in at least one of the RF tag and a computer memory. The method further comprises communicating with the RF tag to identify the location of the carrier unit. The method further comprises identifying the location of at least one of the plurality of mail units based at least in part on the location of the carrier unit. Another embodiment is a system configured to perform an embodiment of the method.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/484,371, filed Jul. 2, 2003, which is incorporated by reference inits entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to systems and methods of materialshandling. More particularly, the present invention relates to systemsand methods of tracking items such as mail in transit.

2. Description of the Related Art

In a mail service, it is necessary to transport a large number of items.The transportation of those items requires the proper sorting of thoseitem, based on, for example, their destination.

Typically, outgoing mail items are sorted at progressive higher levelsof organization. For example, individual letters are generally sortedinto a tray holding letters destined for a particular destination city(e.g., Boston). That tray, together with other trays, will be directedto carriers, sometimes referred to as rolling stock. Each carrier holdsmultiple trays and/or mail sacks and pouches destined for a particulargeographic region (e.g., Los Angeles).

The rolling stock will then be utilized to transport multiple trays to avehicle, to be transported to a mail sorting facility at the intendeddestination. Ultimately, within the intended destination geographicregion, the sorting process will reverse itself. For example, individualmail trays, sacks, and pouches are disaggregated from the rolling stockand routed to their destination locations and individual letters aredelivered to their intended recipient.

When shipping large quantities of mail items, it is desirable toaccurately track shipments. In this regard, it is desirable to tracktrays as they are transported from an origin to a destination. It isfurther desirable to track the weight of shipped mail items and the useof rolling stock capacity, for purposes of being able to increasing theefficiency of the overall transporting process. Thus, a need exists forimproved methods of tracking shipments.

SUMMARY OF CERTAIN EMBODIMENTS

The system, method, and devices of the invention each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this invention as expressed bythe claims which follow, its more prominent features will now bediscussed briefly. After considering this discussion, and particularlyafter reading the section entitled “Detailed Description of Embodiments”one will understand how the features of this invention provideadvantages that include, for example, providing a method for trackingitems during transit.

One embodiment is a method of tracking a plurality of items duringtransfer from a source location to a destination. The method comprisesassociating information identifying the plurality of items with a radiofrequency (RF) tag that identifies a carrier unit. The method furthercomprises storing said associated information in at least one of the RFtag and a computer memory. The method further comprises communicatingwith the RF tag to identify the location of the carrier unit. The methodfurther comprises identifying the location of at least one of theplurality of items based at least in part on the location of the carrierunit.

Another embodiment is a system for tracking a plurality of items duringtransfer from a source location to a destination. The system comprises acarrier unit configured to transport the plurality of items. The systemfurther comprises an RF tag coupled to the carrier unit. The RF tag isconfigured to store information associated with each of the plurality ofitems. The system further comprises a processing station incommunication with the RF tag. The processing station is configured toidentify the location of at least one of the plurality of items based atleast in part on the location of the carrier unit.

Another embodiment is a method of tracking utilization of a plurality ofmail units. The method comprises receiving data indicative of theoccupancy level of the plurality of mail units, each being designated toa transport unit. The method further comprises determining the occupancylevel of the transport unit based, at least in part, on the occupancylevel of the plurality of the mail units. The method further comprisesproviding data indicative of the space available in the transport unit.The method further comprises determining data indicative of theefficiency of utilizing the transport unit based, at least in part, onthe occupancy level of the transport unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram depicting one embodiment of a system fortracking the location of an item.

FIG. 2 a is a functional block diagram of a plurality of trays such asthe tray of FIG. 1.

FIG. 2 b is a functional block diagram of an exemplary multiple traycarrier.

FIG. 2 c is a functional block diagram of the exemplary multiple traycarrier of FIG. 2 b having the trays of FIG. 2 a loaded thereon.

FIG. 3 is a flow chart illustrating one embodiment of a method oftracking the location of an item using, for example, the system depictedin FIG. 1.

FIG. 4 is a flow chart illustrating one embodiment of a method oftracking the multiple tray carrier of FIG. 2 c.

FIG. 5 is a flow chart illustrating one embodiment of a method ofidentifying stale mail using, for example, the system depicted in FIG.1.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following detailed description is directed to certain specificembodiments of the invention. However, the invention can be embodied ina multitude of different ways as defined and covered by the claims. Inthis description, reference is made to the drawings wherein like partsare designated with like numerals throughout.

As used herein, mail units are groups of mail items destined for acommon destination, for example, a particular city. Mail units aretypically transported in a container, or tray. To enable tracking of theprogress of the trays and, e.g., easily identify the destination of thetrays, trays typically receive labels that have printed thereon barcodes and human readable text. It is to be appreciated that whilecertain embodiments are discussed herein with respect to a tray, theterm “tray,” as used herein, is intended to include any unit containerof mail, including a tray, a sack, or a pouch.

FIG. 1 is a block diagram depicting one embodiment of a system 100 fortracking the location of an item, such as a tray 105. In one embodiment,the tray may be configured to store letters or flat mail. The tray maycomprise a substantially rigid material, e.g., fiber board. In anotherembodiment, the tray may comprise a flexible container such as a nylonpouch. An RFID tag 110 is affixed to the tray 105. The RFID tag 110 isin wireless communication with the RFID reader 120. The reader 120 iscoupled to a relay station 130, which relays data through a data network140 to a processing station 150. The reader 120 is configured to send aninterrogation signal, which when received, causes the tag 110 to respondby transmitting an identification signal. The identification signalcomprises an identification number associated with the tag 110.Typically, this identification number is unique to the tag 110. Thisidentification number is sometimes referred to as a “license platenumber.”

The RFID tag 110 may be active or passive. Passive tags typicallycomprise a transistor, antenna, and a coil. In one embodiment, the TAG110 comprises an integrated circuit. Passive tags are powered by thetransmitted interrogation signal of the reader 120. The passive tag 110may comprise a backscatter tag. In one embodiment, the backscatter tag110 transmits its signal by using the transistor to amplitude modulatethe carrier signal that is received by the coil. In an alternativeembodiment, the RFID tag 110 may comprise microscopic size particles orstructures that passively reflect electromagnetic energy in a unique andquantifiable manner in response to an interrogation signal received bythe antenna. Such embodiments comprise chipless devices, e.g., includingneither an integrated circuit nor discrete electronic components such asthe transistor or coil. One such embodiment of an RFID tag 110 comprisesdevices manufactured by Inkode USA of Vienna, Va. In another embodiment,the RFID tag 110 may comprise a device operating on surface acousticwave principles.

Active tags typically comprise a transistor, coil, antenna, and battery.In addition to providing more power for use in transmitting, active tagsmay support encrypted responses. In one embodiment, active tags 110 mayalso respond to particular interrogation signals by storing orretrieving data from a memory.

In one embodiment, the RFID tag 110 is associated with the tray 105 byapplying label stock that is advantageously embedded with RFID tags. Theidentifier of the RFID 110 confers upon each label so constructed aunique identification number. In one embodiment, the RFID tag 110comprises a passive, read-only tag. In one embodiment, it is desirableto configure the RFID tag 110 with a short read range, for example, inthe range of about 5 feet. In other embodiments, the tag 110 may have arange of 1, 2, 3, 4, 6, 7, 8, 9, or 10 feet. In other embodiments, thetag 110 may have a range of over 10 feet. An advantage of a short readrange is that it prevents the unintended reading of other labels in aprocessing facility.

There are a number of advantages to utilizing RFID tags 110 over barcodes within labels. The RFID tag 110 may be “read” even where the labelis not visible, and thus can be read through containers made ofcorrugated fiberboard, canvas, or nylon, or other light obstructivematerial. The RFID tag 110 also does not need to be oriented in aparticular direction for reading.

The label stock may comprise discrete sheets of labels, or, preferably,continuous feed type label stock. The label stock may comprise a plasticor paperboard material. The RFID tag 110 may either be affixed to, orembedded within the tray label stock. In one embodiment, the tag 110 isincorporated into the material of the tag during manufacturing.

A plurality of readers 120 may be placed at different locations in theprocessing facility such that approximate location of the tag 110 may bedetermined by which reader or readers 120 receive the identificationsignal from the tag 110. While one reader 120 is depicted in theembodiment depicted in FIG. 1, it is to be appreciated that embodimentsof the system 100 may comprise sets of readers 120 including from one tohundreds of readers. Exemplary embodiments of such networks of readers120 for tracking an article using RFID tags are discussed in more detailin U.S. Pat. No. 6,211,781, entitled “METHOD AND APPARATUS FOR TRACKINGAND LOCATING A MOVEABLE ARTICLE,” issued on Apr. 3, 2001, and U.S. Pat.No. 6,480,108, also entitled “METHOD AND APPARATUS FOR TRACKING ANDLOCATING A MOVEABLE ARTICLE,” issued on Nov. 12, 2002, each of which isincorporated by reference in its entirety.

In one embodiment, the processing station 150 may comprise a computer(e.g., a server) configured to run a software sorting module to directthe printing of the labels to be placed on the trays 105. In anotherembodiment, standalone processor may execute the sorting module andcommunicate with the processing station 150. The sorting moduleassociates each label with a destination (such as a city name, zip code,or other geographical unit). In a processing facility, the destinationmay correspond to a cell or stacker machine. The destination of the tray105 and the identifier of the tag 110 are recorded proximate to printingthe label. The destination and other information associated with thelabel may be communicated to the processing station 150. In oneembodiment, human readable text is also placed on the label. Inaddition, a bar code may also be placed on the label.

In one embodiment, the RFID tag 110 affixed to the label comprises abackscatter RFID tag. For example, the RFID tag 110 may comprisereflective aluminum silica crystal, which are stable when stored forlong periods of time and have a sufficiently low cost so as to be usedin consumable, single-use labels, such as mail tray labels. It is to beappreciated, however, that any type of RFID tag 110 may be affixed tothe label. Moreover, in one embodiment, the RFID tag 110 may be embeddedin the tray 105. The sort program may control a label printer forprinting information on the labels. The printer may be attached to thereader 120. The tag reader 120 receives the identifier of the tag 110 inthe blank label. The sort program relates the identifier of the tag 110to a destination assigned by a sort plan. The assigned destination mayinclude a corresponding mail bin or stacker.

The reader 120 generally comprises an antenna and a receiver circuittuned to receive the information transmitted by the tag 110. In oneembodiment, the reader 120 comprises a transmitter configured totransmit an interrogation signal. Upon receiving the interrogationsignal, the RFID tag 110 generally responds with its identificationsignal. As noted above, an exemplary embodiment of the reader 120 may beobtained from Inkode USA. The reader 120 may generate the interrogationsignal such that it includes sufficient power or other signalcharacteristics for powering or activating any of the embodiments ofpassive or active tags described herein. The reader 120 may alsotransmit commands or additional data to the tag 110 in the interrogationsignal. Active RFID tags 110 may respond to such commands by storing theadditional data, e.g., the tray weight or destination, within anassociated memory. The reader 120 may transmit a corresponding commandto signal the active tag 110 to transmit the additional data from itsassociated memory to the reader 120.

In one embodiment, the relay station 130 may comprise the reader 120, anantenna 125, and a network interface configured to communicate with thenetwork 140. The relay station 130 relays information from the tagreader 120 to the network 140. The relay station 130 may alsocommunicate commands received from the network 140 to the reader 120. Inone embodiment, the reader 120 and the relay station 130 may be anintegrated device. In another embodiment, the reader 120 may be in datacommunication with the relay station 130 using a peripheral connectioninterface, such as a serial port, a parallel port, Universal Serial Bus(USB), or any other similar wired/wireless data interface. In oneembodiment, the relay station 130 may comprise a mobile computingdevice, e.g., a personal digital assistant (PDA).

The network 140 may comprise wired or wireless networks, for example,one or more of the following networks: the Internet, Intranets, LocalArea Networks (LAN), or Wide Area Networks (WAN). In addition, theconnectivity to the network 140 may be, for example, remote modem,Ethernet (IEEE 802.3), Token Ring (IEEE 802.5), Fiber DistributedDatalink Interface (FDDI) Asynchronous Transfer Mode (ATM), WirelessEthernet (IEEE 802.11), or Bluetooth (IEEE 802.15.1).

The processing station 150 may comprise a processor and a networkinterface for coupling the station 150 to the network 140. Theprocessing station 150 may also comprise a storage medium (not shown),e.g., a memory or a disk drive. In one embodiment, the processor may beembedded or a part of a computer (e.g., a server) that interfaces withthe network 140. The processing station 150 may also comprise softwaremodules run on the process to provide storage and control functions tothe system 100. For example, the software modules may include a databasemodule configured to store data on the storage medium. This databasemodule may be accessible to components (not shown) for viewing orgenerating reports describing the data in the storage medium. Such datamay include the identifiers of tags 110 and other information associatedwith each tag 110, including the destination of the tray 105 carryingthe tag.

In one embodiment, the database module is configured to storeinformation associated with the tag, including: information about thetype of container on which the tag 110 is affixed, the class of mailtherein contained, the label creation date, and a label expiration date.The particular length of the expiration period may be varied as desired,and may be related to the expected period of time that the tray 105 isexpected to be in the mailstream. In one embodiment, this period of timemay vary relative to the respective class of the mail.

In one embodiment, the software modules comprise a decision moduleconfigured to determine the presence or absence of stale mail based atleast partly on information provided by the database module. Stale mailcomprises mail that remains within the postal system after its scheduleddelivery date, or expected time in the mailstream. By associating anexpiry date with a tag 110, stale mail may be identified when a reader120 reads the tag 110 after that date. Once identified, the stale mailmay receive priority processing to expedite delivery and to thusminimize further delays.

FIG. 2 a is a functional block diagram depicting a plurality of trays105 such as the tray 105 of FIG. 1. It is to be appreciated that FIG. 2a depicts a functional representation of the tray 105 and does notdepict or restrict the physical characteristics of the tray 105 or anyother component. At the end of the conveyor line in the processingfacility, the trays destined for a particular geographic unit, e.g., acity, zip code, or carrier route, are moved onto a multiple traycarrier. Multiple tray carriers typically comprise wheels, and are thuscommonly referred to in the collective as rolling stock.

FIG. 2 b is a functional block diagram of an exemplary multiple traycarrier 220. It is to be appreciated that FIG. 2 b depicts a functionalrepresentation of the multiple tray carrier 220 and does not depict orrestrict the physical characteristics of the multiple tray carrier 220or any other component. The multiple tray carrier 220 comprises an RFIDtag 230 and is configured to hold a plurality of the trays 105. In oneembodiment, the multiple tray carrier 220 comprises the RFID tag 230, asupport frame, shelves that are configured to hold the tray 150, andwheels. Multiple tray carriers 220 are commonly referred to collectivelyas rolling stock.

In one embodiment, the carrier tag 230 comprises an active RFID tag thatis configured to store or identify information, e.g., the identifier ofthe tag 110 of each tray 105 carried by the multiple tray carrier 220.However, in another embodiment, the carrier tag 230 may comprise both apassive RFID tag and an active RFID tag. The passive tag may, forexample, identify the multiple tray carrier 220, while the active tagmay, for example, store the identifiers of the tags 110 of trays loadedonto the multiple tray carrier 220. In one embodiment, the active tag230 also has a substantially longer read range than the passive tags 110in the labels of the tray 105. One embodiment of the active carrier tag230 comprises devices manufactured by ID Systems, Inc, such as theFlextag™ system. In another embodiment, the carrier tag 230 comprises apassive tag. Moreover, embodiments of the carrier tag 230 may compriseany of the types of devices described above with respect to the tag 110.

As discussed with reference to FIG. 1, in one embodiment, the reader 120transmits data (e.g., the identity or weight of the trays 105 loadedonto the carrier 220) to the active tag 230 for storage. In oneembodiment, the reader 120 transmits the data to the tag 230 along witha command in the interrogation signal directing the tag 230 to store thedata. The relay station 130 may transmit the data from the processingstation 150 to the reader 120.

FIG. 2 c is a functional block diagram of the exemplary multiple traycarrier 220 of FIG. 2 b having the trays 105 of FIG. 2 a loaded thereon.It is to be appreciated that FIG. 2 c depicts a functionalrepresentation of the multiple tray carrier 220 and its functionalassociation with the tray 105 and does not depict or restrict thephysical characteristics or relationship of any components. Theplurality of trays 105 on the multiple tray carrier 220 may thus becollectively tracked during transport via the RFID tag 230. In oneembodiment, the multiple tray carrier 220 has sufficient capacity toload approximately forty (40) trays. This advantageously reduces thetotal number of items that are tracked. Further, in one embodiment,lower cost passive RFID tags are advantageously used to track the itemsthat are tracked in larger numbers, e.g., the tray 105, while activetags are used for items that are tracked in smaller numbers, e.g., themultiple tray carriers. For example, using such an embodiment, a workeror machine in the field may read characteristics relating to thecollection of trays, e.g., their weight, from the active RFID tag 230without need for that worker or machine to be in communication with theprocessing station 150.

FIG. 3 is a flow chart illustrating one embodiment of a method 300 oftracking the location of an item using, for example, the system depictedin FIG. 1. The method 300 begins at step 302 where a label, including orotherwise coupled to the tag 110, is printed. Next at step 304, thelabel is applied to the tray 105. Moving to step 306, the reader 120receives the identifying signal of the label tag 110. Next at step 310,the sorting module associates the tray 105 with the identifier. Thesorting module also transmits the identifier of the tag 110 andinformation relating to the tray 105, such as its destination, to thedatabase module of the processing station 150. Proceeding to step 312,the database module stores the destination, expiration date, and otherinformation associated with the tray 105.

Next at step 314, the tray 105 is loaded with, for example, mail items.As discussed above, information associated with the mail items, e.g.,the class of the mail may be associated with the tag 110 by the databasemodule. Moving to step 316, the tray 105 continues through the traytransportation/sorting process by, typically, placing the tray 105 ontoa conveyer belt of some type. The conveyer belt may comprise, forexample, a powered roller line or other mechanized take-away line. Theconveyer moves the tray 105 through a processing facility for sortingand distribution. In some instances, the conveyer apparatus has multipleexits, and includes diverters or the like to permit the directing oftrays to different run-outs, or exit points.

Moving to step 320, a scale weighs the tray 105. In one embodiment, theconveyor moves the tray 105 over an in-line scale to weigh the tray 105.Next at step 322, the reader 120 associated with the scale reads theidentification of the tag 110 of the tray 105 on the scale and sends theidentifier to the processing station 150. The scale may communicate theweight to the processing station 150 directly, or to the relay station130 associated with the reader 120. Proceeding to step 324, theprocessing station 150 stores the weight of the tray 105 in associationwith the identifier of the tag 110 on the tray 105. The tray 105 may beweighed at any point along the processing line, depending, for example,on when in the processing steps the particular processing line makesreference to the weight.

Moving to step 326, the reader 120 receives the identifier of the tray105. In one embodiment, one or more readers 120 are positioned atselected positions along one or more conveyers. The short read range ofpassive tags 110 may be exploited to determine the proximate location ofthe tag 110 and its attached tray. In one embodiment, the location isdetermined based at least partly on which of the readers 120 receive asignal from the tag at a given time. In another embodiment, the locationis determined at least partly based on the timing of receipt of thesignal by each of the readers 120. The antennae of the readers 120 maybe positioned, for example, above or below the conveyer. The reader 120may be directly coupled to its antenna, or the antenna may be placed ata different location than the reader and attached by any desired link toits antenna. As discussed above, each reader 120 is in communicationwith the processing station 150 via the relay station 130 and thenetwork 140.

Next at step 330, the position of the tray 105 is stored on theprocessing station 150. The approximation of the position may be basedon the location of the reader 120 receiving the identifier of the tag110, or on a calculation based on the position two or more readers 120that receive the identification signal from the tag 110. Other methodsknown in the art of locating an RF-transmitting object may also be used,such as those discussed in the previously incorporated U.S. Pat. No.6,480,108, entitled “METHOD AND APPARATUS FOR TRACKING AND LOCATING AMOVEABLE ARTICLE.” It is to be appreciated that steps 326 and 330 may beperformed at any number of selected locations within a sorting or othertransit facility. For example, trays 105 may be tracked before or aftertransfer points or sorting stations along the conveyer belt to confirmthat the trays 105 are being transported to the correct destination.

Finally, at a step 332, when, for example, the tray 105 reaches anendpoint of the conveyer, the tray 105 is removed from the conveyer forfurther processing. In particular, the tray 105 may be placed onto themulti-tray carrier 220 for further processing as described below withreference to FIG. 4.

It is to be appreciated that depending on the embodiment, the acts orevents of the method 300, and all other methods described herein, may beperformed in any sequence, may be added, may be merged, or may be leftout all together (e.g., not all acts or events are necessary for thepractice of the method) unless specifically and clearly statedotherwise. Moreover, unless clearly stated otherwise, acts or events maybe performed concurrently rather than sequentially.

FIG. 4 is a flow chart illustrating one embodiment of a method 400 oftracking the multiple tray carrier of FIG. 2 c. In one embodiment, themethod 400 of FIG. 4 follows or continues from the method 300 of FIG. 3.Beginning at step 402, the reader 120 reads the identifier of the RFIDtag 230 of the multi tray carrier 220 and communicates this identifierto the processing station 150. The multi tray carrier 220 is typicallylocated at conveyer exit points, where trays are typically removed fromthe conveyer and loaded into the multiple tray carrier 220. As notedabove, each multiple tray carrier 220 holds multiple trays 105 destinedfor a particular destination, such as Southern California or aparticular post office. In one embodiment, a human or robotic movermoves the trays 105 from the conveyor to the carrier 220. In order toidentify to the mover which carrier 220 the mover is placing the trayon, the mover may also receive the identifier of the carrier 220, e.g.,from the reader 120. The robotic mover may include or have access to amemory to store this identifier. In another embodiment, a human user mayreceive and store the identifier in an electronic device that is incommunication with the reader 120.

Next at step 404, the human or robotic mover reads the tray identifierfrom the tray 105. In one embodiment, the mover uses a bar code readerto receive the identifier of the tray 105 from the label. In anotherembodiment, the RFID reader 120 is located so as to receive only theidentifier of the RFID tag 110 for the particular tray 105 to be loaded.In one embodiment, the bar code reader or the RFID tag reader 120 sendsthe identifier to the processing station 150. As each tray 105 isreceived by the mover for loading, the bar code reader or the RFID tagreader 120 may also transmit the identifier of the tray 105 to themover. The mover for tray 105 may store the identifier of the tray 105.In one embodiment, the mover may associate the identifier of the tray105 with the identifier of the carrier 220 and send this information tothe processing station 150. In another embodiment, the processingstation 150 may be configured to recognize this relationshipautomatically by matching the location of the tray 105 as it reaches theend of the conveyer with the location of the multi tray carrier 220. Theprocessing station 150 may determine the location of each of the tray105 and the carrier 220 by determining the position of the respectiveRFID tags 110 and 230.

Next at step 406, the mover loads the tray 105 onto the multi traycarrier 220. The mover may communicate to the processing station 150that the tray 105 has been loaded. Moving to step 410, the processingstation 150 stores the identifier of the tray 105 and the identifier ofthe multi tray carrier 220 so as to associate the tray 105 with thecarrier 220. In one embodiment, the storage medium stores theidentifiers of the trays 105 and identifiers of the multi tray carriers220 in a table or other data structure that associates each of the trays105 with the respective multi tray carrier 220 onto which each tray 105is loaded. The processing station 150 may also store additionalinformation relating to the carrier 220. For each carrier 220, thisinformation may include, for example, whether the carrier 220 is loadedwith a tray 105 of a particular type, whether the carrier 220 is loadedwith trays 105 containing one or mixed classes of mail, the weight andvolume occupied within each tray 105, the total weight and volumeoccupied within the trays 105 loaded onto the carrier, a capacityutilization of the carrier 220, and an intended destination of each tray105. The capacity utilization of the carrier 220 may be expressed as orcharacterized by a capacity utilization in a cubic unit of measurement(e.g., cubic feet), e.g., the total volume occupied within the trays 105loaded on the carrier 220 divided by the total volume capacity of thetrays 105 loaded onto the carrier 220. In one embodiment, the databasemodule of the processing station 150 communicates this data to thestorage medium.

Next at step 412, the processing station 150 communicates the identifierof the tray 105 to the reader 120. The reader 120 then transmits theidentifier to the RFID tag 230 of the carrier 220, which stores thisdata. In another embodiment, the mover communicates the identifier ofthe tray 105 to the reader 120 which then sends this identifier to theRFID tag 230 of the carrier 220. In yet another embodiment, the reader120 that receives the identifier of the tag 110 communicates theidentifier of the tray 105 directly to the carrier tag 230. In anotherembodiment, the identifier of the tray 105 is not stored on the carriertag 230, but is merely communicated to the processing station 150, whichstores this information. In such an embodiment, the carrier tag 230 maycomprise a passive tag.

The carrier tag 230 stores the identifier of the tray 105 into itsattached memory. In addition, the processing station 150, through reader120, may also communicate other information to the tag 230 for storage.This other information may include, for example, whether the carrier 220is loaded with a container of a particular type, whether the carrier 220is loaded with trays containing one or mixed classes of mail, the weightand capacity volume of each tray, the total weight and volume of traysloaded onto the carrier, a capacity utilization of the carrier 220, andan intended destination of each tray.

With such embodiments, it will be appreciated that tracking each of theplurality of trays 105 on the multi-tray carrier 220 is reduced totracking the single multi-tray carrier 220. This desirably reduces thecomplexity and quantity of items in the tracking process. Further, in anembodiment in which the multi-tray carrier 220 comprises the active RFID230, additional information, such as the weight or destination of thetrays, may be stored with the carrier 220. This enables any worker orrobot with an embodiment of the reader 120, such as a handheld reader,to easily determine, for example, the weight of the trays on the carrier220, even when the worker or robot is not in communication with theprocessing station 150. Thus, a delivery worker in the field can easilydetermine information relating to a carrier 220 without relying on aprinted label, which may not be visible, e.g., when loaded on a vehicle.

Proceeding to step 414, the reader 120 may periodically receive andcommunicate the tag 230 of the rolling stock 220 to the processingstation 150 to track its progress through the system, avoid misroutingof stock, and the like. Preferably, tags 230 support radiolocationschemes such as TDMA and/or CSMA to determine the physical locations ofsuch RFID tagged rolling stock 220 to help prevent it from beingmisplaced and/or lost among a multiplicity of identical pieces ofrolling stock 220. Tag readers 120 for rolling stock 220 may bepositioned high on walls, within or above doorways through which rollingstock passes, at loading docks, at vehicle entrances, or at otherlocations. Mobile tag readers 120, for example handheld units, may alsobe utilized.

Moving to step 416, the processing station 150 may track the capacityutilization of each multi tray carrier 220. In addition, as the carriers220 are loaded onto mail transport equipment (MTE), e.g., trucks, fortransport, the processing station 150 may track the capacity utilizationof the MTE. In one embodiment, software modules executing on theprocessing station 150 may use the information in the storage mediumrelating to the carriers 220 to produce various calculations of capacityutilization data. Capacity utilization data may include datarepresenting the occupied and remaining storage capacity for the trays105, containers 220, or MTE. Capacity utilization may be calculated interms of weight, volume occupied, or both. In one embodiment,determining capacity utilization of a carrier comprises dividing thenumber of trays 105 loaded onto each carrier 220 by the capacity of thecarrier 220 in terms of the number of trays 105. In another embodiment,the capacity utilization of a carrier 220 may be expressed as orcharacterized by a weighted average of the capacity utilization of eachtray 105 loaded onto the carrier divided by the total volume capacity ofthe carrier 220. In one embodiment, the capacity utilization of the MTEmay be expressed as or characterized by, for example, the weightedaverage of the volume capacity utilization of each carrier 220 that isloaded onto the MTE divided by the total carrier volume capacity of theMTE.

The processing station 150 may store the capacity utilization data totrack the utilization of particular MTEs. Software modules may read,collate, aggregate, or report the capacity utilization data. A planner,either a human or a software module, may use this stored capacityinformation to identify under-utilized MTE. For example, in oneembodiment, the capacity utilization data may identify for the plannerthat the MTE for a particular destination have low capacity utilizationbecause the trays 105 are individually under-utilized in terms of volumeoccupied. The planner may then further utilize tracking of such capacitydata to identify adjustments in the processing of the trays 105 toincrease capacity utilization of the trays 105. The planner maysimilarly utilize capacity utilization data, e.g., in terms of number oftrays 105 per carrier 220, to reduce the number of carriers 220 forparticular destinations. Further, the planner may use MTE capacityutilization data in terms of number of carriers per MTE to adjust thesize of MTE, e.g., truck, assigned to particular destinations orspecific trips to improve MTE efficiency. 511 FIG. 5 is a flow chartillustrating one embodiment of a method 500 of identifying staleshipments using, for example, the system depicted in FIG. 1. The method500 begins at step 510, in which the processing station 150 receives theidentifier for a tray. Moving to step 512, a software module associatedwith the processing station 150, retrieves the expiration date for thetray 105. Proceeding to step 514, the software module compares theexpiration date to a processing date, e.g., the current date or a futuredate of, e.g., 1-3 days after the current date, to determine if theexpiration date has passed. If the expiration date has not passed, themethod 500 returns to the step 510 to process the next tray in thesystem. If the date has passed, then the method 500 proceeds to step516. Next at step 516, the processing station 150 generates a signalidentifying that the tray 105 is stale. In one embodiment, theprocessing station 150 transmits the signal to an indicator device thatdirects a person to the carrier 220 that contains the stale tray and toremove the stale tray to expedited processing. In another embodiment,the signal is directed to a sorting module that directs the stale trayappropriately, e.g., for expedited processing. In yet anotherembodiment, the processing station 150 directs the signal to a softwaremodule within the processing station 150. The software module may tracksand direct processing of the stale tray. It is to be appreciated thatwhile the method 500 is discussed with respect to the tray 105,corresponding processing may also be performed with respect to themultiple tray carrier 220.

Other embodiments of the systems and methods described herein may beemployed to reduce the complexity and quantity of mail items other thantrays 105. For example, in one embodiment, rather than tracking trays105 with RFID tags, individual items of mail that comprise uniqueidentifiers may also be tracked by tracking a carrier 230 that is loadedwith a plurality of these items. For example, express mail items haveunique identifiers in the form of bar codes. Rather than needing to readthe bar codes of each of a plurality of express mail at each and everylocation where tracking of the express mail items is desired, theindividual express mail items may be loaded onto a carrier unitidentified by a tag 220. Thus, the location the express mail items maybe identified based on the location of the easier to track carrier unit.

While the methods and system as described herein may be utilized, in onepreferred embodiment, in the transportation and sorting of mail items,the systems and methods may also be utilized for the transportation andsorting of other items where efficient and accurate transportation andlife cycle information is required. For example, military equipment,such as artillery projectiles, ammunition containers, propellant chargesand containers for propellant charges, fuzes, and the like may betracked during transport and storage. In such an embodiment, theidentifier of the tag 110 may be associated with information that formsa birth to death data base record for individual artillery munitions.This record may include such artillery ammunition life cycle events asprojectile type (high explosive (HE), smoke, illuminating), model (155mm HE M107 vs. M795) number, production facility, production date andlot number, weight stamp code, packing date, packing mode (rack of threeversus crate of two), repack date, and other data elements.

While the above detailed description has shown, described, and pointedout novel features of the invention as applied to various embodiments,it will be understood that various omissions, substitutions, and changesin the form and details of the device or process illustrated may be madeby those skilled in the art without departing from the spirit of theinvention. As will be recognized, the present invention may be embodiedwithin a form that does not provide all of the features and benefits setforth herein, as some features may be used or practiced separately fromothers. The scope of the invention is indicated by the appended claimsrather than by the foregoing description. All changes which come withinthe meaning and range of equivalency of the claims are to be embracedwithin their scope.

1. A method of tracking a plurality of mail units during transfer from asource location to a destination, the method comprising: associatinginformation identifying the plurality of mail units with a radiofrequency (RF) tag that identifies a carrier unit; storing saidassociated information in at least one of the RF tag and a computermemory; communicating with the RF tag to identify the location of thecarrier unit; and identifying the location of at least one of theplurality of mail units based at least in part on the location of thecarrier unit.
 2. The method of claim 1, wherein the step of associatinginformation comprises matching the carrier unit to each of the pluralityof mail units.
 3. The method of claim 1, wherein the step of associatinginformation comprises receiving an identifier from the RF tag andstoring said identifier in a database that relates the identifier withthe plurality of mail units.
 4. The method of claim 1, wherein the stepof associating comprises receiving an identifier from each of aplurality of RF tags, each identifying one of the plurality of mailunits, and storing the plurality of RF tags in a database that relatesthe plurality of RF tags with the carrier unit.
 5. The method of claim4, wherein the step of reading the identifier comprises sending aninterrogation signal to each of the plurality of RF tags and receivingan identifier from each of the plurality of RF tags.
 6. The method ofclaim 1, wherein the step of storing comprises storing the identifiersof the plurality of mail units into a memory associated with the RF tagthat identifies the carrier unit.
 7. The method of claim 1, furthercomprising loading the mail units onto the carrier unit.
 8. The methodof claim 1, further comprising: receiving an identifier of the carrierunit; receiving an identifier for each of the plurality of mail units;and storing data that associates the identifier of the carrier unit withthe identifier of each of the plurality of mail units.
 9. The method ofclaim 1, wherein the step of storing associated information comprisesstoring in the RF tag at least one of: the weight of at least one of theplurality of mail units, the total weight of the plurality of mailunits, the volume of at least one of the plurality of mail units, thetotal volume of the plurality of mail units, a mail class, an expirationdate, and a destination.
 10. The method of claim 1, wherein the step ofassociating information comprises associating an expiration date with atleast one of the plurality of mail units and the method furthercomprising comparing the expiration date associated with the at leastone of the plurality of mail units to predetermined criteria.
 11. Themethod of claim 1, wherein the step of identifying the location of atleast one of the plurality of mail units comprises identifying thelocation of the RF tag of the carrier unit.
 12. A system for tracking aplurality of mail units during transfer from a source location to adestination, the system comprising: a carrier unit configured totransport the plurality of mail units; an RF tag coupled to the carrierunit, wherein the RF tag is configured to identify the carrier unit andto store information associated with each of the plurality of mailunits; and a processing station in communication with the RF tag,wherein the processing station is configured to identify the location ofat least one of the plurality of mail units based at least in part onthe location of the carrier unit.
 13. The system of claim 12, whereinthe processing comprises at least one of a processor, a computer, aserver, a receiver, a transmitter, a network interface, and a storagemedium.
 14. The system of claim 12, wherein the RF tag comprises anactive RF tag.
 15. The system of claim 12, wherein the processingstation is configured to match each of the plurality of mail units tothe carrier unit.
 16. The system of claim 12, wherein the processingstation is configured to receive an identifier from the RF tag and tostore said identifier in a database that relates the identifier with theplurality of mail units.
 17. The system of claim 12, wherein theprocessing station is configured to receive an identifier from each of aplurality of RF tags, each of the plurality of RF tags identifying oneof the plurality of mail units and wherein the processing station isfurther configured to store the plurality of RF tags in a database thatrelates the plurality of RF tags with the carrier unit.
 18. The systemof claim 17, further comprising a reader configured to send aninterrogation signal to each of the plurality of RF tags and receive anidentifier from each of the plurality of RF tags, wherein the reader isfurther configured to communicate the identifier to the processingstation.
 19. The system of claim 12, wherein processing station isconfigured to store the identifiers of the plurality of mail units intoa memory associated with the RF tag that identifies the carrier unit.20. The system of claim 12, further comprising a mover configured toload the mail units onto the carrier unit.
 21. The system of claim 12,wherein the processing station is further configured to: receive anidentifier of the carrier unit; receive an identifier for each of theplurality of mail units; and store data that associates the identifierof the carrier unit with the identifier of each of the plurality of mailunits.
 22. The system of claim 12, wherein the RF tag is configured tostore at least one of: the weight of at least one of the plurality ofmail units, the total weight of the plurality of mail units, the volumeof at least one of the plurality of mail units, the total volume of theplurality of mail units, a mail class, an expiration date, and adestination.
 23. The system of claim 12, wherein the processing stationis configured to compare an expiration date with at least one of theplurality of mail units.
 24. The system of claim 23, wherein theprocessing station is configured to compare the expiration dateassociated with the at least one of the plurality of mail units topredetermined criteria.
 25. The system of claim 12, wherein theprocessing station is configure to identify the location of carrier unitbased at least in part on identifying the location of the RF tag. 26.The system of claim 12, wherein the RF tag comprises an RFidentification (RFID) tag.
 27. A method of tracking utilization of aplurality of mail units, the method comprising: receiving dataindicative of the occupancy level of the plurality of mail units, eachbeing designated to a transport unit; determining the occupancy level ofthe transport unit based, at least in part, on the occupancy level ofthe plurality of the mail units; providing data indicative of the spaceavailable in the transport unit; determining data indicative of theefficiency of utilizing the transport unit based, at least in part, onthe occupancy level of the transport unit.
 28. The method of claim 27,wherein receiving the data comprises receiving at least one volumemeasurement from a radio frequency identification (RFID) tag.
 29. Themethod of claim 27, wherein each of the plurality of mail unitscomprises a mail carrier comprising a plurality of mail trays.
 30. Themethod of claim 29, wherein the transport unit comprises a truck. 31.The method of claim 27, wherein determining data indicative of theefficiency comprises determining a volume utilization rate or percentageof the plurality of mail units.